Inhalation of aerosol powders from dry powder inhalers (DPI's) is a convenient way of delivering drugs to patients, such as asthmatics. Current DPI's typically make use of small amounts of micronized drug blended with large amounts of carrier particles, such as a lactose carrier, to facilitate efficient delivery of the drug to the lungs. The efficiency and reproducibility of delivery of such blends is dependent on the patient's lung function and can be effected by parameters such as inspiratory flow rate and/or volume. Existing DPI's can be reservoir based, such as those capable of storing and delivering large numbers of doses to patients, as well as receptacle based, such as those utilizing capsules or blisters.
Patients that could benefit from drugs delivered via a DPI often times do have compromised or reduced lung function, which can alter, reduce, or delay the efficiency of delivery or therapeutic onset of the drug. Conditions leading to such compromised lung function include asthma, COPD, anaphylaxis, emphysema, and other forms of respiratory distress. Other factors such as a patient's age (i.e. children or elderly patients), history (i.e. smoking, chemical exposure) and other conditions can also lead to a reduction of inspiratory flow rate and/or volume.
A need exists to be able to efficiently and reproducibly deliver therapeutic agents to the lungs of such compromised patients. This would optimally utilize low masses of dry particles capable of being delivered via a single breath-activated step, especially at low inspiratory flow rates and/or low inspiratory volumes. Also, a need exists to deliver a large fraction of the mass of such particles from the DPI to the pulmonary system of a compromised patient.